Osta is also a Mobile City, except it's an "unfinished" one.
According to a blue-haired boy's introduction, before the "cataclysm" arrived, the people here indeed tried to build a new Mobile City centered around this hill. However, the problem arose afterward when Wira's mother became pregnant and gave birth to a child.
Yet, for Wira's mother, she did not wish to have a child because she was physically not well at the time, and it seemed she didn't like her husband either. But no one cared about her wishes at the time when the world had already begun to "distort," fewer and fewer children were being born, so she was almost forcibly required to give birth to that child.
Therefore, when the child was born, people crowded around to rescue the baby, abandoning the mother—it seemed a reasonable choice to them. After all, there were hardly any more children being born in this world, and the sickly mother was about to die anyway; it was unlikely she could give birth again.
